Zero Tolerance is a 1994 video game developed by Technopop and published by Accolade exclusively for the Sega Mega Drive/Genesis video game console. It was one of the few Mega Drive/Genesis first person shooters, besides Bloodshot and the Duke Nukem 3D port. Due to the limitations of the hardware, the player's view of the 3D environment was restricted to a fraction of the screen, with the player's HUD, a map of the surrounding area, and the player character's ID card comprising the rest of the screen space. Still, it featured impressive visual effects for its time and especially for the Genesis, a system with hardware that lacked much of the necessary scaling and rotation technologies normally needed to create even the most rudimentary appearance of 3D environments (such as rival Super NES' built-in "Mode 7" technology and "Super FX Chip" add-on). In fact, the smoothness and speed at which Zero Tolerance ran was said to rival many of the lower-end versions of Doom available at the time.
In the future, mankind has made great advances in interstellar travel and subsequently colonised the Solar System. The extrasolar settlements, research outposts, mines, commercial colonies, and spacecraft and space stations throughout the Solar System are protected over by a mighty, interstellar military conglomerate named the Planet Defense Corps.
When Europa-1, the flagship of the Planet Defense Corps, is attacked by an unknown yet lethal aggressor of apparently extraterrestrial nature, the Planet Defense Corps call in Zero Tolerance, an elite strike squad of five speciality-trained commandos. A recording of the last transmission from Europe-1 reveals extensive fire damage to the warship, almost total casualties and otherworldly creatures hunting the few remaining survivors of the attack. Also, the nuclear cooling system of Europa-1 has been damaged by small arms fire, and core breach caused by overheating will destroy the starship in a matter of hours.
As a member of the Zero Tolerance squad, the player is ordered during the crisis briefing to infiltrate Europa-1 before it explodes. His mission is to completely eliminate the mysterious alien aggressor from within, and also the transformed humans of Europa-1 they have "infected", in the next few hours to erase all evidence of the attack and the alien intruders.
Zero Tolerance is made up of 40 levels spanning three separate areas: the space warship Europe-1, an abandoned merchant freighter, the heavily fortified central command building for the Planet Defense Corps, and the sub-basement areas of that building. The object of the game is to kill all of the enemies on a level and then proceed to the exit, which is either a staircase or elevator leading down to the next level.
However, nothing prevents the player from heading straight towards the exit without killing all of the enemies. If this is done, the player is simply not given any passwords until the entire area is finished.
Once a character is killed that character will be listed as "deceased", and becomes unavailable for playing. The player can choose from a total of five different characters; once they are all deceased the game is over.
Zero Tolerance was widely considered an enjoyable game with great visuals and a unique addition to the Genesis' library. Even though it was overshadowed by the other big first-person shooters of its day, most notably Doom, it is a cult favorite and there is still currently a large presence of Zero Tolerance fans amongst the retro gaming community. The game, as well as its unfinished sequel, have been deemed by developer Technopop to be publicly distributable as freeware.